Hypodermic syringes are utilized in the medical field to inject fluids into the body or to remove fluids from the body. At present, syringe bodies are sold commercially in a number of different sizes. However, common to each size or capacity of syringe body is a distal end which has a standard needle engaging thread-like projection. Similarly, hypodermic needles are manufactured in a variety of diameters and lengths for various purposes. Commercially available needles, however, no matter the length or diameter, all have a standard hub which engages with the standard threads on the various syringe bodies. Through this standardization, different size needles can be utilized with different size syringe bodies, thus avoiding the need for a different set of needles for each size of syringe.
Currently, the prevalent practice in the industry is to attach the needle to the desired syringe body, utilize the needle, then cap the needle and discard the syringe along with the capped needle. Typically, the needle cap is slightly larger in diameter than the needle. The process of capping the needle after use subjects the health care workers to accidental pricking from the needle. This in turn creates a risk of infection from a contaminated needle which is highly undesirable especially for such diseases as AIDS.
Various attempts to protect health care workers from accidental pricking have been proposed. One such method is to provide a slidable sleeve over the syringe body which after use of the syringe can be slid into place over the needle such as shown in U.S. Pat. No. 4,425,120. This device would have the drawback of limiting or distorting visibility and measurement of the syringe contents. Also, the device would not be easily moldable.
Others have suggested the provision of a retractable needle which after use is pulled back into the body of the syringe to thereby eliminate exposure of the sharp needle tip. One such attempt is shown in U.S. Pat. No. 4,026,287 wherein the syringe body is constructed such that the needle is formed into the front of the syringe, and the front of the syringe is connected to the side wall by an area of serration. After use of the syringe, the plunger engages the front portion of the syringe body and force is applied to break the serrations, after which the front of the syringe and needle can be retracted into the syringe body. Such design appears to offer a structure which is likely to break when the needle is in the patient, if the structure is such that it can be easily broken to retract the needle. U.S. Pat. No. 4,507,117 discloses a needle which forms an integral part of a slidable piston which can be moved within the syringe to expose the needle or to retract the needle. This device will not accept standard needles. U.S. Pat. No. 4,675,005 illustrates a needle which is adapted to be threaded into the syringe body and which may be engaged by a plunger in order to retract the needle. A number of variations of design are presented which have undesired dead volume or undesirable connecting apparatus. U.S. Pat. No. 4,650,462 discloses a retractable needle syringe apparatus of rather complex construction. The attempts to provide for a retractable needle have all required special construction of the syringe body and the needle. These patents require special needle constructions and have not been commercially produced. U.S. Pat. No. 4,710,170 discloses a retractable syringe needle apparatus of complex construction which utilizes standard needles. None of the patents are believed to disclose a device which has been commercially accepted.
Thus, there has been a continuing need for a syringe device which provides the ability to retract a needle into the syringe body which can utilize standard needles, is simple in construction, manufacture, and assembly, is simple to use, and which does not provide significant dead volume.